Administrator Guide

Protocol Data Units

Configuration information is exchanged in the form of type, length, value (TLV) segments. The below figure

shows the chassis ID TLV.

• Type — Indicates the type of field that a part of the message represents.

• Length — Indicates the size of the value field (in byte).

• Value — Indicates the data for this part of the message.

Figure 63. Type, Length, Value (TLV) Segment

TLVs are encapsulated in a frame called an LLDP data unit (LLDPDU), which is transmitted from one LLDP-

enabled device to its LLDP-enabled neighbors. LLDP is a one-way protocol. LLDP-enabled devices (LLDP

agents) can transmit and/or receive advertisements, but they cannot solicit and do not respond to

advertisements.

There are five types of TLVs (as shown in the below table). All types are mandatory in the construction of an

LLDPDU except Optional TLVs. You can configure the inclusion of individual Optional TLVs.

Table 36. Type, Length, Value (TLV) Types

Type TLV Description

End of LLDPDU Marks the end of an LLDPDU.

Chassis ID The Chassis ID TLV is a mandatory TLV that identifies the chassis

containing the IEEE 802 LAN station associated with the transmitting

LLDP agent.

Port ID The Port ID TLV is a mandatory TLV that identifies the port

component of the MSAP identifier associated with the transmitting

LLDP agent.

Link Layer Discovery Protocol (LLDP) 550